Semiconductor device manufacturing method comprising a metal pattern and laser modified regions in a cutting region

ABSTRACT

To divide a semiconductor wafer by stealth dicing, a test pad in a cutting region and an alignment target are collectively arranged along one side in a width direction of the cutting region, and a laser beam for forming a modified region is irradiated to a position away in plane from the test pad and the alignment target Am. In this manner, defects in cutting shape in a cutting process of a semiconductor wafer using stealth dicing can be reduced or prevented.

This is a continuation application of U.S. Application Ser. No.12/092,850, filed May 7, 2008, now allowed, the contents of which arehereby incorporated by reference into this application.

TECHNICAL FIELD

The present invention relates to a method of manufacturing asemiconductor-device and a semiconductor device, and in particular, itrelates to a dicing technology of semiconductor wafer.

BACKGROUND ART

In recent years, along with reductions in size and weight of mobiledevices as typified by cellular phones and digital cameras, andinformation storage media as typified by memory cards, semiconductorchips embedded in these have been made thinner. For this reason, while adicing process obtains individual thin semiconductor chips by cutting athin semiconductor wafer, chipping tends to occur in the semiconductorchips due to their thinness in a dicing process using a blade dicingmethod, thereby causing a problem of significant decrease in bendingstrength of the thin semiconductor chips. Moreover, although alow-dielectric-constant film (so-called Low-k film) having a dielectricconstant lower than that of silicon oxide is used for an insulating filmbetween wiring layers of a semiconductor chip in view of improving anoperation speed of a semiconductor device, such a Low-k film is brittleand tends to peel off, and may have subtle air bubbles therein, andtherefore may not be able to be cut well through blade dicing.

To get around these problems, stealth dicing has attracted attentions asa new dicing method. In stealth dicing, the inside of a semiconductorwafer is radiated with laser beam to selectively form a modified layer,and the semiconductor wafer is cut with taking this modified layer as adivision starting point. In this method, even an extremely thinsemiconductor wafer having a thickness on the order of 30 μm can bedirectly cut off without physically applying stress, thereby reducingchipping and suppressing reduction in bending strength of thesemiconductor chips. Also, regardless of the thickness of semiconductorwafers, high-speed dicing over 300 mm per second can be performed,thereby also increasing throughput. Therefore, for making semiconductorchips thinner, stealth dicing is an indispensable technology.

Such stealth dicing technology is described in, for example, JapanesePatent Application Laid-Open Publication No. 2004-221286 (PatentDocument 1). In paragraph 0022 and FIG. 1 of this Patent Document 1, astructure is disclosed in which a wiring layer is provided on both sidesof a test pad in a region between chips. These wiring layers are not forelectrical coupling, but are dummy patterns for homogenizing a radiationregion of laser beams and causing the laser beams to be easily absorbed.Further, in paragraph 0023 of this Patent Document 1, a method isdisclosed in which a laser beam is irradiated to the region to melt forcutting the semiconductor wafer in dividing the semiconductor wafer.Furthermore, in paragraph 0024 of this Patent Document 1, a method isdisclosed in which, a melting-processing region is formed throughmultiphoton absorption by placing a focal point of the laser beam at theinside of the semiconductor wafer, and then the semiconductor wafer isdiced by cracking method or expansion method upon dividing thesemiconductor wafer.

And, for example, in Japanese Patent Application Laid-Open PublicationNo. 2005-340426 (Patent Document 2), a stealth dicing technology isdisclosed in which, after a groove is formed on a test bonding pad on amain surface of a semiconductor wafer, a tape is adhered on the mainsurface of the semiconductor wafer and a laser beam is irradiated fromthe back surface of the semiconductor wafer to form a modified layerinside of the semiconductor wafer, and then the tape is expanded todivide the semiconductor wafer into individual semiconductor chips withtaking the modified layer as the starting point.

Still further, for example, in Japanese Patent Application Laid-OpenPublication No. 2005-32903 (Patent Document 3), a stealth dicingtechnology is disclosed in which, after a test electrode pad and thelike on a main surface of a semiconductor wafer is removed by a blade, alaser beam is radiated from the main surface of the semiconductor waferto form a modified layer inside of the semiconductor wafer, and then adicing tape is expanded to divide the semiconductor wafer intoindividual semiconductor chips with taking the modified layer as thestarting point.

-   Patent document 1: Japanese Patent Laid-Open Publication No.    2004-221286, (paragraphs 0022-0024 and FIG. 1)-   Patent document 2: Japanese Patent Laid-Open Publication No.    2005-340426-   Patent document 3: Japanese Patent Laid-Open Publication No.    2005-32903

DISCLOSURE OF THE INVENTION

Meanwhile, the inventors of the present invention have found out thefollowing problems in the stealth dicing described above.

First, the inventors have studied the case of using expansion method individing a semiconductor wafer through stealth dicing. In this expansionmethod, a resin sheet having a semiconductor wafer adhered thereto isexpanded in a direction from the center of the semiconductor wafer toits outer periphery to divide the semiconductor wafer into individualsemiconductor chips. While a test pad formed of, for example, aluminumis arranged in a dicing region, when the test pad is expanded to be cut,a beard-like conductor line is disadvantageously formed on thecutting-plane portion in the expansion method.

Accordingly, the inventors have adopted a bending method in place of theexpansion method. In this bending method, a semiconductor wafer is bentby applying a force in a direction crossing a main surface of thesemiconductor wafer to divide the semiconductor wafer into individualsemiconductor chips. In this method, the above-described problem offormation of a beard-like conductor line can be reduced. However, asshown in FIG. 65, new problems occur such that, a crack CRK occurs so asto bypass the test pad because an insulating-layer portion where no testpad is present is mechanically weaker than the test portion, and causesa cut at the insulating-layer portion, and also the cutting linemeanders because it is unsettled at the insulating-layer portion betweenthe test pads of the dicing region. In particular, when theabove-described Low-k film is used, which is brittle and tends to peeloff, a defect in shape occurs at a dividing portion of the Low-k filmeven with the use of the bending method, thus making it impossible toneatly cut the wafer.

Moreover, according to the technique of Patent Document 1, since thewiring layer is formed of a metal with strength higher than that of theinsulating layer on a cutting line between the chips, there is a problemthat it is disadvantageously impossible to neatly cut the wafer. Stillfurther, since the wiring layer is formed on each side of the test padso that a laser beam is easily absorbed, a space between adjacent chipshas to be widened, and thus the number of chips that can be arranged onthe surface of the semiconductor wafer is disadvantageously decreased.

An object of the present invention is to provide a technology capable ofreducing or preventing a defect in cutting shape in a cutting process ofsemiconductor wafer using stealth dicing.

The above and other objects and novel characteristics of the presentinvention will be apparent from the description of this specificationand the accompanying drawings.

The typical ones of the inventions disclosed in this application will bebriefly described as follows.

The present invention comprises a step of irradiating a laser to a sideof a test pad in a separation region for individual semiconductor chipson a semiconductor wafer to form a modified region to serve as adivision starting point at a laser irradiation position inside thesemiconductor wafer, and then performing dicing of the semiconductorwafer into the individual semiconductor chips by the bending method.

Further, the present invention comprises a step of irradiating a laserto a test pad in a separation region for individual semiconductor chipson a semiconductor wafer to form a groove or hole serving as a divisionstarting point of the test pad in a step of cutting the semiconductorwafer.

Moreover, the present invention comprises a step of irradiating a laseron separation regions of individual semiconductor chips on asemiconductor wafer to form a modified region to serve as a divisionstarting point at the laser irradiation position inside thesemiconductor wafer, and a step of removing a test pad of thesemiconductor wafer.

The effects obtained by typical aspects of the present invention will bebriefly described below.

That is, by irradiating a laser to a side of a test pad in a separationregion for individual semiconductor chips on a semiconductor wafer toform a modified region serving as a division starting point at a laserirradiation position inside the semiconductor wafer, and then performingdicing on the semiconductor wafer into the individual semiconductorchips by a bending method, it is possible to reduce or prevent a defectin a cut shape in a cutting process of a semiconductor wafer usingstealth dicing.

BRIEF DESCRIPTIONS OF THE DRAWINGS

FIG. 1 is a flow chart of a manufacturing process of a semiconductordevice according to an embodiment of the present invention;

FIG. 2 is a plan view of a whole main surface of a semiconductor waferafter a front-end process 100 of FIG. 1;

FIG. 3 is a cross-sectional view taken along the line X1-X1 of FIG. 2;

FIG. 4 is an enlarged plan view of main parts of the semiconductor waferof FIG. 2;

FIG. 5 is an enlarged plan view of a region R1 of FIG. 4;

FIG. 6 is a cross-sectional view taken along the line X2-X2 of FIG. 5;

FIG. 7 is a cross-sectional view of main parts of the semiconductorwafer, showing a detailed example of the cross-sectional structure ofthe semiconductor wafer of FIG. 6;

FIG. 8 is a plan view of a whole jig having the semiconductor waferaccommodated therein;

FIG. 9 is a cross-sectional view taken along the line X3-X3 of FIG. 8;

FIG. 10 is a cross-sectional view of the semiconductor wafer and the jigduring a back-surface processing step;

FIG. 11 is a cross-sectional view of the semiconductor wafer and the jigafter the back-surface processing step;

FIG. 12 is a plan view of main parts of the semiconductor wafer after alaser irradiation step;

FIG. 13 is a cross-section along the line X4-X4 of FIG. 12;

FIG. 14 is a plan view of main parts of another example of thesemiconductor wafer after the laser irradiation step;

FIG. 15 is a plan view of main parts of still another example of thesemiconductor wafer after the laser irradiation step;

FIG. 16 is a cross-sectional view of main parts of the semiconductorwafer before a dividing step;

FIG. 17 is a cross-sectional view of main parts of the semiconductorwafer during the dividing step;

FIG. 18 is an enlarged cross-sectional view of main parts of thesemiconductor wafer of FIG. 17;

FIG. 19 is a cross-sectional view of main parts of the semiconductorwafer during the dividing step;

FIG. 20 is a plan view of a whole semiconductor chip cut out from thesemiconductor wafer;

FIG. 21 is a plan view of semiconductor chips and a wiring board after adie bonding step;

FIG. 22 is a cross-sectional view taken along the line X5-X5 of FIG. 21;

FIG. 23 is a plan view of the semiconductor chips and the wiring boardafter a wire bonding process;

FIG. 24 is a cross-sectional view taken along the line X6-X6 of FIG. 23;

FIG. 25 is a cross-sectional view of a semiconductor device after asealing step;

FIG. 26 is a plan view of a whole semiconductor chip of a semiconductordevice according to another embodiment of the present invention;

FIG. 27 is a plan view of an example of mounting the semiconductor chipof FIG. 26;

FIG. 28 is a plan view of main parts of a semiconductor wafer during asemiconductor device manufacturing process according to anotherembodiment of the present invention;

FIG. 29 is a cross-sectional view taken along the line X8-X8 of FIG. 28;

FIG. 30 is a cross-sectional view taken along the line X9-X9 of FIG. 28;

FIG. 31 is a cross-sectional view of the semiconductor wafer taken alongthe line X8-X8 of FIG. 28, showing a state of irradiating a laser beamof a first round;

FIG. 32 is a cross-sectional view of the semiconductor wafer taken alongthe line X9-X9 of FIG. 28, showing a state of irradiating the laser beamof the first round;

FIG. 33 is a plan view of main parts of the semiconductor wafer afterthe laser-beam irradiation step of the first round;

FIG. 34 is a cross-sectional view taken along the line X10-X10 of FIG.33;

FIG. 35 is a cross-sectional view taken along the line X11-X11 of FIG.33;

FIG. 36 is a cross-sectional view of the semiconductor wafer taken alongthe line X8-X8 of FIG. 28, showing a state of irradiating a laser beamof a second round;

FIG. 37 is a cross-sectional view of the semiconductor wafer taken alongthe line X9-X9 of FIG. 28, showing a state of irradiating the laser beamof the second round;

FIG. 38 is a plan view of a whole semiconductor chip cut out from thesemiconductor wafer;

FIG. 39 is a cross-sectional view taken along the line X12-X12 of FIG.38;

FIG. 40 is a flow chart of a semiconductor device manufacturing processaccording to another embodiment of the present invention;

FIG. 41 is a cross-sectional view of a semiconductor wafer after a WSSmounting step of FIG. 40;

FIG. 42 is a cross-sectional view of the semiconductor wafer afterback-surface grinding and polishing steps of FIG. 40;

FIG. 43 is a cross-sectional view of main parts of the semiconductorwafer during a laser irradiation step of FIG. 40;

FIG. 44 is a plan view of the semiconductor wafer and a jig after awafer mounting step and a WSS peeling-off step of FIG. 40;

FIG. 45 is a cross-sectional view taken along the line X13-X13 of FIG.44;

FIG. 46 is a cross-sectional view of main parts of the semiconductorwafer during a TEG processing step of FIG. 40;

FIG. 47 is a cross-sectional view of main parts of the semiconductorwafer after the TEG processing step of FIG. 40;

FIG. 48 is an enlarged cross-sectional view of main parts of thesemiconductor wafer during a dividing step of FIG. 40;

FIG. 49 is a plan view of a whole semiconductor chip cut out from thesemiconductor wafer in the dividing step of FIG. 40;

FIG. 50 is a cross-sectional view taken along the line X14-X14 of FIG.49;

FIG. 51 is a cross-sectional view of main parts of a semiconductor waferduring a laser irradiation step in a semiconductor device manufacturingprocess according to another embodiment of the present invention;

FIG. 52 is a cross-sectional view of main parts of the semiconductorwafer during a TEG processing step after the state of FIG. 51;

FIG. 53 is a plan view of main parts of the semiconductor wafer afterthe TEG processing step;

FIG. 54 is a cross-sectional view taken along the line X15-X15 of FIG.53;

FIG. 55 is an enlarged cross-sectional view of main parts of thesemiconductor wafer during a dividing step after the step of FIG. 53;

FIG. 56 is a plan view of a whole semiconductor chip cut out from thesemiconductor wafer in the dividing step of FIG. 55;

FIG. 57 is a cross-sectional view taken along the line X16-X16 of FIG.56;

FIG. 58 is a cross-sectional view of main parts of the semiconductorwafer during a TEG processing step in a semiconductor devicemanufacturing process according to another embodiment of the presentinvention;

FIG. 59 is a cross-sectional view of main parts of the semiconductorwafer after the TEG processing step of FIG. 58;

FIG. 60 is an enlarged cross-sectional view of main parts of thesemiconductor wafer during a dividing step after the state of FIG. 59;

FIG. 61 is a cross-sectional view of main parts of a semiconductor waferduring a TEG processing step in a semiconductor device manufacturingprocess according to still another embodiment of the present invention;

FIG. 62 is an enlarged cross-sectional view of main parts of thesemiconductor wafer during a dividing step after the state of FIG. 61;

FIG. 63 is an enlarged cross-sectional view of main parts of thesemiconductor wafer during the TEG processing step;

FIG. 64 is a cross-sectional view of a semiconductor chip and a wiringboard, showing a modification example of FIG. 24;

FIG. 65 is a cross-sectional view of main parts showing a state of adirection in which a crack is developed when a semiconductor wafer isdivided;

FIG. 66 is an illustrative diagram for describing a problem which occursdue to removing a TEG by using a dicing saw after forming a fracturedlayer in a semiconductor wafer by laser radiation;

FIG. 67 is a cross-sectional view of main parts of a semiconductor waferduring a semiconductor device manufacturing process according to anotherembodiment of the present invention;

FIG. 68 is a cross-sectional view of main parts of the semiconductorwafer during the semiconductor device manufacturing process continuedfrom FIG. 67;

FIG. 69 is a cross-sectional view of main parts of the semiconductorwafer during the semiconductor device manufacturing process continuedfrom FIG. 68;

FIG. 70 is a cross-sectional view of main parts of the semiconductorwafer during the semiconductor device manufacturing process continuedfrom FIG. 69;

FIG. 71 is a cross-sectional view of main parts of the semiconductorwafer during the semiconductor device manufacturing process continuedfrom FIG. 70;

FIG. 72 is a cross-sectional view of main parts of the semiconductorwafer during the semiconductor device manufacturing process continuedfrom FIG. 71;

FIG. 73 is an illustrative diagram for describing a problem which occursdue to laser radiation from a main surface side of the semiconductorwafer after TEG is removed by using a dicing saw;

FIG. 74 is a plan view of a semiconductor wafer according to anotherembodiment of the present invention;

FIG. 75 is an enlarged plan view of main parts of the semiconductorwafer of FIG. 74;

FIG. 76 is a cross-sectional view of main parts of the semiconductorwafer when removing TEG of FIG. 75;

FIG. 77 is a plan view showing a state of dividing a semiconductor waferaccording to another embodiment of the present invention;

FIG. 78A is a plan view of a whole semiconductor wafer, showing aspecific state of the semiconductor wafer dividing step described inFIG. 77, and FIG. 78B is a cross-sectional view taken along the lineX17-X17 of FIG. 78A;

FIGS. 79A and 79B are enlarged cross-sectional views of main parts ofthe semiconductor wafer during the dividing step; and

FIGS. 80A to 80C are cross-sectional views of a semiconductor waferduring a semiconductor device manufacturing process according to anotherembodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

In the embodiments described below, the invention will be described in aplurality of sections or embodiments when required as a matter ofconvenience. However, these sections or embodiments are not irrelevantto each other unless otherwise stated, and the one relates to the entireor a part of the other as a modification example, details, or asupplementary explanation thereof.

Also, in the embodiments described below, when referring to the numberof elements (including number of pieces, values, amount, range, and thelike), the number of the elements is not limited to a specific numberunless otherwise stated or except the case where the number isapparently limited to a specific number in principle. The number largeror smaller than the specified number is also applicable. Further, in theembodiments described below, it goes without saying that the components(including element steps) are not always indispensable unless otherwisestated or except the case where the components are apparentlyindispensable in principle. Similarly, in the embodiments describedbelow, when the shape of the components, positional relation thereof,and the like are mentioned, the substantially approximate and similarshapes and the like are included therein unless otherwise stated orexcept the case where it can be conceived that they are apparentlyexcluded in principle. The same goes for the numerical value and therange described above. Also, components having the same function aredenoted by the same reference symbols throughout the drawings fordescribing the embodiments, and the repetitive descriptions thereof areomitted as possible. Hereinafter, embodiments of the present inventionwill be described in detail with reference to the accompanying drawings.

First Embodiment

A method of manufacturing a semiconductor device according to a firstembodiment will be described according to a flow of FIG. 1.

First, in a front-end process 100, a semiconductor wafer (hereinafter,referred to as a wafer) having a main surface and a back surface thatare opposite to each other along a thickness direction is provided, anda plurality of semiconductor chips (hereinafter, referred to as chips)are formed on the main surface (device formation surface) of the wafer.This front-end process 100 is also called a wafer process or waferfabrication, in which chips (integrated circuits (elements and wirings))are formed on the main surface of the wafer so that an electric test canbe performed with a probe and others. The front-end process includes afilm formation process, an impurity introduction (diffusion or ionimplantation) process, a photolithography process, an etching process, ametallizing process, a cleaning process, and an inspection processbetween these processes.

FIG. 2 is a plan view of a whole main surface of a semiconductor wafer1W after the front-end process 100. FIG. 3 is a cross-sectional viewtaken along the line X1-X1 of FIG. 2. FIG. 4 is an enlarged plan view ofmain parts of the semiconductor wafer W1 of FIG. 2. FIG. 5 is anenlarged plan view of a region R1 of FIG. 4. FIG. 6 is a cross-sectionalview taken along the line X2-X2 of FIG. 5. FIG. 7 is a cross-sectionalview of main parts of the semiconductor wafer 1W, showing a detailedexample of a cross-sectional structure of the semiconductor wafer 1W ofFIG. 6. Here, a reference symbol N in FIG. 2 denotes a notch.

The wafer 1W is made of a semiconductor thin plate having asubstantially circular shape in a plan view and having a diameter on theorder of, for example, 300 mm, as shown in FIG. 2 and FIG. 3. The wafer1W has a main surface on which a plurality of chips 1C having, forexample, a rectangular shape in a plan view, are arranged in a matrix.

Each chip 1C has formed thereon a memory circuit such as a flash memory,for example. Also, at one end of each chip 1C in a longitudinaldirection, as shown in FIG. 4 and FIG. 5, a plurality of bonding pads(hereinafter, bonding pad will referred to as pad) 1LB are arranged inline along a side at one end side of the chip 1C in the longitudinaldirection. The pads 1LB are external terminals for drawing outelectrodes of the memory circuit (integrated circuit) formed on the chip1C to the outside of the chip 1C, and are electrically connected toelements for forming the memory circuit through wirings. Here, inaddition to the memory circuit, a logic circuit such as a microprocessormay be formed as an integrated circuit on the chip 1C.

A cutting region (chip separation region) CR is arranged around theperiphery of each chip 1C. On this cutting region CR, as shown in FIGS.4 and 5, test (TEG: Test Element Group) pads 1LBt and an alignmenttarget Am are arranged. The test pad 1LBt is formed in, for example, asquare in a plan view and has a size of, for example, the order of 50μm×50 μm. These pads 1LBt are external terminals for drawing outelectrodes of a TEG element to the outside of the chips 1C, and areelectrically connected to the TEG elements through wirings. The TEGelements are elements for use in measuring and testing electriccharacteristics of elements formed in the chips 1C. The alignment targetAm is formed in, for example, a cross shape in a plan view, but may bealso formed in an L shape or a dot shape. The alignment target Am is apattern for use in alignment between a manufacturing apparatus such as alight-exposing apparatus, and the chips 1C on the wafer 1W.

A semiconductor substrate (hereinafter, referred to as a substrate) 1Sconfiguring the wafer 1W as described above is made of, for example,single crystal silicon (Si), and has a main surface on which an elementand a wiring layer 1L are formed. A thickness D1 of the wafer 1W (atotal sum of the thickness of the substrate 1S and the thickness of thewiring layer 1L) (refer to FIG. 3) in this stage is, for example, on theorder of 775 μm.

On the wiring layer 1L, as shown the in FIG. 6 and FIG. 7, an interlayerinsulating film 1Li, wirings, the pads (external terminals) 1LB, thetest pads 1LBt, the alignment target Am, and a surface protective film(hereinafter, referred to as a protective film) 1Lp are formed. Theinterlayer insulating film 1Li comprises a plurality of interlayerinsulating films 1Li1, 1Li2, and 1Li3.

The interlayer insulating film 1Li1 has formed therein insulating films2 a, 2 b. The insulating films 2 a, 2 b are alternately deposited on thesubstrate 1S. The insulating film 2 a is formed of, for example, aninsulating film of inorganic system, such as silicon oxide (SiO₂ or thelike). The insulating film 2 b is formed of, for example, siliconnitride (Si₃N₄ or the like). The insulating film 2 b is thinner than theinsulating film 2 a, and has a function as an etching stopper, forexample. The interlayer insulating film 1Li1 has formed therein plugs(contact plugs) PL1 and PL2 and a wiring L1.

The plugs PL1 and PL2 are formed by burying a conductive film in holesH1, H2, respectively. A conductive film forming each of the plugs PL1,PL2 has a main conductive film and a barrier metal film formed so as tocover peripheries (a bottom surface and side surface) of the mainconductive film. The main conductive film is formed of, for example,tungsten (W) and is thicker than the barrier metal film. The barriermetal film is formed of, for example, titanium nitride (TiN), tungstennitride (WN), tantalum nitride (TaN), tantalum (Ta), titanium (Ti),tungsten (W), titanium tungsten (TiW), or a multilayered film of thesemetal films. The wiring L1 is assumed to be a buried wiring, forexample. That is, this wiring L1 is formed by burying a conductive filmin a wiring trench T1 formed on the insulating films 2 a, 2 b. Thestructure of the conductive film of the wiring L1 is identical to thoseof the plugs PL1, PL2.

The interlayer insulating film 1Li2 has formed thereon insulating films3 a, 3 b, 3 c, 3 d, and wirings L2, L3. The insulating film 3 a isformed of, for example, carbon silicon (SiC), having a function of anetching stopper. The insulating film 3 a is formed so as to be thinnerthan the insulating films 3 b, 3 c, 3 d.

The insulating film 3 b is formed of a low-dielectric-constant film(Low-k film), such as an organic polymer or organic silica glass, havinga dielectric constant lower than the dielectric constant of siliconoxide (for example, 3.9-4.0), in view of increasing the operation speedof the semiconductor device. The insulating film 3 b is formed so as tobe thicker than the insulating films 3 a, 3 c, 3 d.

As the organic polymer (a complete-organic low dielectric interlayerinsulating film), for example, SiLK (manufactured by The Dow ChemicalCompany of the United States, relative dielectric constant=2.7, uppertemperature limit=490° C. or higher, dielectric breakdown withstandvoltage=4.0-5.0 MV/Vm) or a polyallylether (PAE) based material FLARE(manufactured by Honeywell Electronic Materials of the United States,relative dielectric constant=2.8, upper temperature limit=400° C. orhigher) can be used. This PAE-based material has a feature of a highbasic performance and an excellent mechanical strength, thermalstability, and low cost.

As the organic silica glass (SiOC-based material), for example, HSG-R7(manufactured by Hitachi Chemical Co., Ltd., relative dielectricconstant=2.8, upper temperature limit=650° C.), Black Diamond(manufactured by Applied Materials, Inc. of the United States, relativedielectric constant=3.0 to 2.4, upper temperature limit=450° C.), orp-MTES (developed by Hitachi, Ltd., relative dielectric constant=3.2)can be used. Other SiOC-based materials include, for example, CORAL(manufactured by Novellus Systems, Inc. of the United States, relativedielectric constant=2.7-2.4, upper temperature limit=500° C.) andAurora2.7 (manufactured by ASM Japan K.K., relative dielectricconstant=2.7, upper temperature limit=450° C.)

And, other low-dielectric-constant film materials include, for example,complete-organic SiOF-based materials such as FSG; HSQ (hydrogensilsesquioxane) base materials; MSQ (methyl silsesquioxane) basedmaterials; porous HSQ based materials; porous MSQ materials; or porousorganic materials.

The above HSQ base materials include, for example, OCD T-12(manufactured by Tokyo Ohka Kogyo Co., Ltd., relative dielectricconstant=3.4 to 2.9, upper temperature limit=450° C.), FOx (manufacturedby Dow Corning Corp. of the United States, relative dielectricconstant=2.9), or OCL T-32 (manufactured by Tokyo Ohka Kogyo Co., Ltd.,relative dielectric constant=2.5, upper temperature limit=450° C.)

The above MSQ-based material include, for example, OCD T-(manufacturedby Tokyo Ohka Kogyo Co., Ltd., relative dielectric constant=2.7, uppertemperature limit=600° C.), LKD-T200 (manufactured by JSR Corporation,relative dielectric constant=2.7-2.5, upper temperature limit=450° C.),HOSP (manufactured by Honeywell Electronic Materials of the UnitedStates, relative dielectric constant=2.5, upper temperature limit=550°C.), HSG-RZ25 (manufactured by Hitachi Chemical Co., Ltd., relativedielectric constant=2.5, upper temperature limit=650° C.), OCL T-31(manufactured by Tokyo Ohka Kogyo Co., Ltd., relative dielectricconstant=2.3, upper temperature limit=500° C.), and LKD-T400(manufactured by JSR, relative dielectric constant=2.2-2, uppertemperature limit=450° C.)

The above porous HSQ base materials include, for example, XLK(manufactured by Dow Corning Corp. of the United States, relativedielectric constant=2.5-2), OCL T-72 (manufactured by Tokyo Ohka KogyoCo., Ltd., relative dielectric constant=2.2-1.9, upper temperaturelimit=450° C.), Nanoglass (manufactured by Honeywell ElectronicMaterials of the United States, relative dielectric constant=2.2-1.8,upper temperature limit=500° C. or higher), or MesoELK (manufactured byAir Products and Chemicals, Inc. of the United States, relativedielectric constant=2 or lower).

The above porous MSQ base materials include, for example,HSG-6211×(manufactured by Hitachi Chemical Co., Ltd., relativedielectric constant=2.4, upper temperature limit=650° C.), ALCAP-S(manufactured by Asahi Kasei Industry Co., relative dielectricconstant=2.3-1.8, upper temperature limit=450° C.), OCL T-77(manufactured by Tokyo Ohka Kogyo Co., Ltd., relative dielectricconstant=2.2-1.9, upper temperature limit=600° C.),HSG-6210×(manufactured by Hitachi Chemical Co., Ltd., relativedielectric constant=2.1, upper temperature limit=650° C.), and silicaaerogel (manufactured by Kobe Steel Ltd., relative dielectricconstant=1.4-1.1).

The above porous organic materials include, for example, PolyELK(manufactured by Air Products and Chemicals, Inc. of the United States,relative dielectric constant=2 or lower, upper temperature limit=490°C.)

The above SiOC-based materials and SiOF-based materials are formedthrough CVD (Chemical Vapor Deposition), for example. By way of example,Black Diamond mentioned above is formed through CVD using mixed gas oftrimethylsilane and oxygen, for example. Also, p-MTES mentioned above isformed through CVD using mixed gas of methyltriethoxysilane and N₂O, forexample. Other low-dielectric-constant insulating materials are formedthrough coating, for example.

The insulating film 3 c described above is formed of, for example,silicon oxide. This insulating film 3 c has functions of, for example,ensuring mechanical strength of a low-dielectric-constant film at thetime of CMP (Chemical Mechanical Polishing), surface protection, andensuring moisture resistance. This insulating film 3 c is formed so asto have a thickness substantially same with that of the insulating film3 d. The material of the insulating film 3 c is not limited to siliconoxide as described above, but can be variously modified. For example, asilicon nitride (Si_(x)N_(y)) film, a carbon silicon film, or a carbonnitride silicon (SiCN) film may be used. Such a silicon nitride film,carbon silicon film, or carbon nitride silicon film can be formedthrough, for example, plasma CVD. An example of a carbon silicon filmformed through plasma CVD is BLOk (manufactured by AMAT (AppliedMaterials Inc.), relative dielectric constant=4.3).

The insulating film 3 d is formed of, for example, carbon nitridesilicon. This insulating film 3 d has a function as an etching stopper,as well as a function of suppressing or preventing diffusion of copperforming a main conductive film of the wirings L2, L3.

The wirings L2 and L3 are assumed to be buried wirings. That is, thesewirings L2, L3 are formed by burying a conductive film in wiringtrenches T2, T3. As with the wiring L3, the conductive film of thewirings L2, L3 has a main conductive film and a barrier metal filmformed so as to cover peripheries (a bottom surface and side surface) ofthe main conductive film. The main conductive film is formed of copper(Cu), for example, and is formed thicker than the barrier metal film.The material of the barrier metal film is identical to the material ofthe plugs PL1, PL2. The wiring L3 is electrically connected to thewiring L2 via a hole H3. The conductive film in a wiring trench T3 ofthe wiring L3 and the conductive film in a hole H3 are integrallyformed.

The interlayer insulating film 1Li3 is formed of silicon oxide, forexample. The interlayer insulating film 1Li3 has formed therein a plugPL3. This plug PL3 is formed by burying a conductive film in a hole H4.The conductive film forming the plug PL3 is same with those of the plugsPL1, PL2.

This interlayer insulating film 1Li3 has formed thereon wirings, thepads 1LB, 1LBt, and the alignment target Am. These wirings, pads 1LB,1LBt, and alignment target Am are formed of, for example, a metal filmsuch as aluminum. These uppermost wirings, pads 1LB, 1LBt, and othersare covered with a protective film 1Lp formed on an uppermost layer ofthe wiring layer 1L. The protective layer 1Lp is formed of amultilayered film including an inorganic insulating film 1Lp1 such assilicon oxide; an inorganic insulating film 1Lp2 such as silicon nitridedeposited on the inorganic insulating film 1Lp1; and an organicinsulating film 1Lp3 such as polyimide resin further deposited on theinorganic insulating film 1Lp2. On a part of this protective film 1Lp,an opening 5 is formed, and parts of the pads 1LB, 1LBt are exposed fromthe opening 5.

Meanwhile, in the first embodiment, the test pads 1LBt (including TEGelements and wirings) and the alignment target Am are arranged on oneside in a width direction (short direction) of the cutting region CR.That is, the test pads 1LBt and the alignment target Am are arranged soas to be shifted from the center of the cutting region CR in the widthdirection. And, cutting lines CL onto which a laser beam is irradiatedat the time of stealth dicing do not pass arrangement lines of the testpads 1LBt and the alignment target Am but pass the sides of the testpads 1LBt and the alignment target Am. That is, the cutting lines CL donot go across the test pads 1LBt and the alignment target Am but passpositions away from the test pads 1LBt and the alignment target Am.

When the cutting lines CL overlap metal patterns such as the test pads1LBt and the alignment target Am, unevenness in mechanical strengthoccurs between a portion where the metal patterns are present and aportion where the metal patterns are not present, and thelow-dielectric-constant film is brittle and tends to peel off, thus thewafer cannot be neatly divided in that case. Also, when the cuttinglines CL overlap metal patterns such as the test pads 1LBt and thealignment target Am, a beard-like conductive substance may remain at acutting portion of any of these metal patterns upon cutting, and thatconductive substance may make contact with a bonding wire or anelectrode to cause a short circuit, and thus there is a problem ofdecreasing reliability and yield of a thin semiconductor device.

With respect to this problem, according to the first embodiment, sincethe cutting lines CL do not overlap the test pads 1LBt and the alignmenttarget Am, the wafer 1W can be neatly cut. And, since the metal patternssuch as the test pads 1LBt and the alignment target Am are not cut, theoccurrence of a beard-like conductive substance as described above canbe prevented. Therefore, reliability and yield of a thin semiconductordevice can be increased.

Further, when the cutting lines CL overlap metal patterns such as thetest pads 1LBt and the alignment target Am and a laser beam isirradiated from the main surface of the wafer 1W at the time of stealthdicing, those pads 1LBt, alignment target Am, and others may cause anobstruction, thereby making it difficult to form a modified region inthe substrate 1S. To get around this problem, according to the presentembodiment, since the cutting lines CL do not overlap the test pads 1LBtand the alignment target Am, even when a laser beam is irradiated fromthe main surface of the wafer 1W at the time of stealth dicing, themodified region, which will be described further below, can be formed onthe substrate 1S in good condition. Thus, flexibility of the laserirradiation can be increased.

Next, in a test process 101 in FIG. 1, a probe is placed on the pads 1LBon each chip 1C and the test pads 1LBt on the cutting region CR on thewafer 1W to perform various inspections regarding electriccharacteristics. This test process is also called a G/W (Goodchip/Wafer) check process, in which the quality of each chip 1C formedon the wafer 1W is electrically determined.

In the subsequent back-end process 102 in FIG. 1, each chip 1C is packedin a sealing body (package) for completion, and includes a back-surfaceprocessing step 102A, a chip dividing step 102B, and an assembling step102C. In the following, these back-surface processing step 102A, chipdividing step 102B, and assembling step 102C will be described in order.

In the back-surface processing step 102A, the wafer 1W is made thinner.First, in the back-surface processing step, the wafer 1W is installed ina jig. FIG. 8 is a plan view of a whole jig 7 having the semiconductorwafer 1W installed therein. FIG. 9 is a cross-sectional view taken alongthe line X3-X3 of FIG. 8. Here, in FIG. 8, the chips 1C on the mainsurface of the wafer 1W are represented by broken lines.

The jig 7 comprises a tape 7 a and a ring (frame body) 7 b. A tape base7 a 1 of the tape 7 a is made of, for example, a plastic material havingplasticity, and has a main surface on which an adhesive layer 7 a 2 isformed. The tape 7 a is firmly adhered to the main surface (chipformation surface) of the wafer 1W by the adhesive layer 7 a 2. If thethickness of the tape 7 a (total sum of the thickness of the tape base 7a 1 and the thickness of the adhesive layer 7 a 2) is too large,handling and peeling-off of the tape 7 a in subsequent steps will bedifficult. Therefore, the tape 7 a for use has a thin thickness, forexample, on the order of 130 to 210 μm. As this tape 7 a, an UV tape ispreferably used, for example. The UV tape is an adhesive tape in which aultraviolet-ray (UV)-curing resin is used as the material of theadhesive layer 7 a 2, and as well as having a strong adhesiveness, theUV tape has a characteristic such that the adhesiveness of the adhesivelayer 7 a 2 abruptly becomes weak when it is irradiated with ultravioletrays (step 102A1).

In the first embodiment, the ring 7 b having stiffness is adhered to theperiphery of the main surface (a surface to which the wafer 1W isadhered) of the tape 7 a. The ring 7 b is a reinforcing member having afunction of supporting the tape 7 a so that the tape 7 a is notdistorted. In view of reinforcement, the ring 7 b is preferably formedof a metal, such as stainless, but may be formed of a plastic materialwith a thickness allowing hardness substantially same to that of metal.Around the periphery of the ring 7 b, notch portions 7 b 1, 7 b 2 areformed. These notch portions 7 b 1, 7 b 2 are used at the time ofhandling the jig 7 and at the time of alignment of the jig 7 and amanufacturing apparatus on which the jig 7 is placed. Also, the notchportions 7 b 1, 7 b 2 are used as catching portions when the jig 7 isfixed to the manufacturing apparatus. Here, the ring 7 b may be adheredto the back surface (a surface opposite to the surface to which thewafer 1W is adhered) of the tape 7 a. Also, the ring 7 b may be adheredeither before adhering the wafer 1W to a tape 37 or after the wafer 1Wis adhered to the tape 7 a.

Then, in a state where the wafer 1W placed on the jig 7, the thicknessof the wafer 1W is measured and, based on the measurement result, theamount of grinding and the amount of polishing are calculated (step102A2). Then, the procedure goes to back-surface grinding (step 102A3)and polishing (step 102A4). FIG. 10 is a cross-sectional view of thesemiconductor wafer 1W and the jig 7 when a back-surface processing stepis performed. FIG. 11 is a cross-sectional view of the semiconductorwafer 1W and the jig 7 after the back-surface processing step isperformed. Here, as shown in FIG. 10, with a grinding/polishing tool 8and a suction stage 9 being rotated, a grinding process and a polishingprocess are performed in sequence on the back surface of the wafer 1Wbased on the abovesaid amount of grinding and the amount of polishing.In this manner, as shown in FIG. 11, the thickness of the wafer 1W ismade very thin (ultrathin), for example, equal to or smaller than 100 μm(here, on the order of 90 μm, for example). As the polishing process, amethod of polishing by using a polishing pad and silica or ChemicalMechanical Polishing (CMP) may be used. Also, etching by using nitricacid and hydrofluoric acid may be used. Here, with the thickness of thechips 1C becoming thinner equal to or smaller than 100 μm, damage andstress, caused on the back surface of the wafer 1W due to the grindingprocess, may decrease bending strength of the chips. In this manner,defects that the chips may break due to a pressure become easy to occurwhen the chips 1C are mounted. Accordingly, the polishing process isperformed after the grinding process, thereby reducing or eliminatingdamage and stress caused on the back surface of the wafer 1W due to thegrinding process. Consequently, the bending strength of the thin chips1C can be increased.

After the back-surface processing step as described above, a vacuumsuction state of the suction stage 9 is released, and then the jig 7holding the wafer 1W is taken out from a back-surface processing device.At this time, in the first embodiment, even the wafer 1W is ultrathin,the tape 7 a can be firmly supported by the ring 7 b. Therefore,handling and carrying the ultrathin wafer 1W is easy. Also, at the timeof handling and carrying, it is possible to prevent the wafer 1W frombreaking or warping. Therefore, the quality of the wafer 1W can beensured. Accordingly, in the first embodiment, with the ultrathin wafer1W being held by the jig 7 at the stage after back-surface processing,the wafer 1W may be conveyed for shipping to another factory (anassembly fab, for example), to which a request for dicing afterback-surface processing and assembly may be made.

Next, the procedure goes to the chip dividing step 102B. Here, first,the jig 7 with the ultrathin wafer 1W being held thereon is carried asit is to a dicing apparatus, and is placed on a suction stage of thedicing apparatus. That is, although it is normally required to perform aprocess of peeling off the tape adhered to the main surface of the wafer1W at the time of back-surface processing and then attaching a dicingtape to the back surface of the wafer 1W (such a process is called awafer mounting process), this wafer mounting process can be omitted inthe first embodiment. Therefore, the semiconductor device manufacturingprocedure can be simplified, thereby reducing the semiconductor devicemanufacturing time. And, since no dicing tape is required, material costcan be reduced, thereby reducing cost of the semiconductor device.

Subsequently, in the first embodiment, with the jig 7 being vacuumsucked, patterns on the main surface of the wafer 1W are recognized byan infrared-operated camera (hereinafter, referred to as an IR camera)from the back surface of the wafer 1W (step 102B1). The patterns includepatterns of the chips 1C and the cutting region CR, metal patterns ofthe pads 1LBt arranged on the cutting region CR, the alignment targetAm, and others, and metal patterns of the pads 1LB arranged in each chip1C. At this time, in the first embodiment, since the wafer 1W is verythin, the state of the patterns on the main surface of the wafer 1W canbe sufficiently observed.

After that, based on the pattern information obtained by the IR camera,alignment (positional correction) of the cutting lines CL is performed.Then, a laser beam (a first laser) LB1 emitted from a laser generatingunit is irradiated from the back-surface side of the wafer 1W with alight-collecting point (focal point) being placed at the inside of thesubstrate 1S, and the laser beam is moved along the cutting lines CLaligned based on the pattern information (step 102B2). FIG. 12 is a planview of main parts of the semiconductor wafer 1W after the laserirradiation step. FIG. 13 is a cross-section taken along the line X4-X4of FIG. 12. By the laser irradiation step, a modified region(optically-damaged portion or a fractured layer) PR is formed inside ofthe substrate 1S in the cutting region CR of the wafer 1W throughmultiphoton absorption. FIG. 12 exemplarily shows a case where a laserbeam LB1 is successively irradiated along the cutting region CR, and themodified region PR is formed so as to successively extend along thecutting region CL.

This modified region PR is formed by heating the inside of the wafer 1Wthrough multiphoton absorption for melting, and serves as a cuttingstarting region of the wafer 1W at the time of the chip dividing steplater. This melt-processed region is in a state of having beenre-solidified after melting, in a midst of state of melting, or in astate of being re-solidified from a melting state. Therefore, it can besaid that the melt-processed region is a phase-changed region or an areain which its crystal structure has been changed. Also, it can be saidthat the melt-processed region is such that, one structure has beenchanged to another structure among a single crystal structure, anamorphous structure, and a polycrystal structure. For example, in thesubstrate 1S part, the melt-processed region means: a region where itssingle crystal structure has been changed to an amorphous structure; aregion where its single crystal structure has been changed to apolycrystal structure; or a region where its single crystal structurehas been changed to an amorphous structure and a polycrystal structure.It is assumed herein that the modified layer PR is amorphous silicon,for example. In addition, here, the laser beam LB1 transmits through theback surface of the wafer 1W to cause multiphoton absorption inside ofthe wafer 1W so as to form the modified region PR, and the laser beamLB1 is hardly absorbed on the back surface of the wafer 1W. Therefore,the back surface of the wafer 1W does not melt.

Here, upon irradiation with the laser beam LB1 as described above, inthe first embodiment, the laser beam LB1 is irradiated to the side ofthe test pads 1LBt in the cutting region CR. That is, the laser beam LB1is irradiated so as not to overlap the pads 1LBt and the alignmenttarget Am in a plane. That is, a division starting point (modifiedregion PR) of the wafer 1W does not overlap the pads 1LBt and thealignment target Am in a plane. In this manner, at the time of cuttingthe wafer 1W, metal patterns, such as the test pads 1LBt and thealignment target Am, are not cut. Therefore, the wafer 1W can be neatlycut. That is, defects in cut shape of the wafer 1W can be reduced orprevented. Also, the occurrence of such a beard-like conductivesubstance as described above can be prevented. Therefore, reliabilityand yield of a thin semiconductor device can be increased.

And, in the case of blade dicing for cutting the wafer 1W with a dicingblade, when the wafer 1W is thin, chipping tends to occur at the time ofcutting, thereby decreasing bending strength of the chips. Therefore, inview of ensuring the quality of the chips 1C, the operation has to beslow (for example, on the order of 60 mm per second or slower dependingon the thickness of the wafer 1W). By contrast, in the first embodiment,only the inside of the wafer 1W is fractured without damaging thesurface of the wafer 1W, thereby minimizing chipping on the surface ofthe chips 1C. Thus, the bending strength of the chips 1C can beincreased. Also, a high-speed cutting process of, for example, 300 mmper second can be performed, thereby increasing throughput.

Furthermore, as described above, if the laser beam LB1 is irradiatedfrom the main surface side of the wafer 1W to a portion of the cuttingregion CR on the main surface of the wafer 1W, that portion may beobstructed by the test pads 1LBt, and therefore the portion cannot besufficiently processed (the modified region PR cannot be sufficientlyformed). By contrast, in the first embodiment, the laser beam LB1 isirradiated from the back surface side of the wafer 1W where any metal,such as the test pads 1LBt, do not present. Therefore, the modifiedregion PR can be excellently formed without causing the above-describeddefects, and the wafer 1W can be neatly cut.

The modified regions PR may be formed in a broken-line (dotted) shape,as shown in FIGS. 14 and 15. FIG. 14 exemplarily shows the case wherethe modified regions PR are arranged in a broken-line (dotted) shapealong the cutting lines CL. That is, the modified regions PR arearranged so as to be intermittently and equally spaced apart from eachother along the cutting lines CL. Since the low-dielectric-constant film(insulating film 3 b) for use as the interlayer insulating film 1Li hasa low thermal conductivity and so heat tends to remain, it may bediscolored by heat at the time of irradiation with the laser beam LB1.Accordingly, by intermittently irradiating the laser beam LB1, theradiation area of the laser beam LB1 can be decreased, therebyminimizing the occurrence of heat due to radiation with the laser beamLB1. Thus, it is possible to prevent or suppress a change in color ofthe low-dielectric-constant film due to heat. And, FIG. 15 exemplarilyshows the case where the modified regions PR are collectively arrangedon portions where it is difficult to divide, such as a crossing portionof the cutting lines CL orthogonal to each other and a portion where TEGfine patterns are collected. Accordingly, even these portions difficultto divide can be easily divided, thereby neatly dividing the wafer 1W.Here, a cross section taken along the line X4-X4 in FIGS. 14 and 15 isidentical to that in FIG. 13. And, examples of irradiation conditions ofthe laser beam LB1 are as follows, but they are not particularlylimited. That is, for example, a light source is a YAG laser at awavelength of 1064 nm; a laser spot diameter is 1 to 2 μm, for example;an irradiation speed is 300 mm/s; and irradiation is performed with 0.7μm spacings. Here, the above light-collecting point is a point at whichthe laser beam LB1 is collected.

Next, the procedure goes to a step of dividing the wafer 1W (step102B3). FIG. 16 is a cross-sectional view of main parts of thesemiconductor wafer 1W before a dividing step is performed. FIG. 17 is across-sectional view of main parts of the semiconductor during 1W whenthe dividing step is performed. FIG. 18 is an enlarged cross-sectionalview of main parts of the semiconductor wafer 1W of FIG. 17. FIG. 19 isa cross-sectional view of main parts of the semiconductor wafer 1Wduring the dividing step.

First, as shown in FIG. 16, the patterns on the main surface of thewafer 1W (in addition to patterns of the chips 1C and the cutting regionCR, metal patterns of the pads 1LBt arranged on the cutting region CR,the alignment target Am, and others, and metal patterns of the pads 1LBarranged in each chip 1C) and the modified regions PR are recognized byan IR camera 12.

Then, a pair of line vacuum chucks 13 is placed on the back surface ofthe tape 7 a on the jig 7. The positions of the line vacuum chucks 13are then aligned based on the positional information obtained by the IRcamera 12. In this state, the tape 7 a is sucked by the pair of linevacuum chucks 13. The pair of line vacuum chucks 13 extends across thewafer 1W (in a direction orthogonal to the paper surface). A tilt isformed to one of the side surfaces of the pair of line vacuum chucks 13that face each other.

After that, as shown in FIGS. 17 and 18, the wafer 1W is bent by movingone of the line vacuum chucks 13 (the left one in FIGS. 17 and 18) sothat it rotates to have its side surface (tilted surface) abut on thefacing side surface of the other line vacuum chuck 13. In this manner,the wafer 1W is cut (divided) at the modified region PR as a divisionstarting point. Then, as shown in FIG. 19, after the one of the linevacuum chuck 13 is returned to the original position, the pair of linevacuum chucks 13 is moved to the next cutting position. Then, the wafer1W is cut in a manner similar to the above. Thereafter, such anoperation is repeated until the surroundings of all chips 1C on thewafer 1W are cut. In the first embodiment, the cutting lines CL do notoverlap the test pads 1LBt and the alignment target Am. Thus, even anexpansion method is used as the dividing method, the metal patterns suchas the test pads 1LBt and the alignment target Am are not cut.Therefore, the occurrence of the beard-like conductive substance asdescribed above can be prevented. However, in the expansion method, asdescribed above, the resin sheet is expanded in a direction from thecenter toward the outer periphery (radially) of the wafer 1W. Therefore,the chips 1C are not separated in a direction that crosses each cuttingline CL (orthogonal direction). In other words, a load (stress) forcutting is not transferred in a direction crossing each cutting line CL.As a result, there is a possibility that the wafer 1W cannot be neatlycut. In some cases, chipping may occur around the periphery of thechips. By contrast, when the bending method is applied, a load forcutting can be transferred in the direction crossing each cutting lineCL. Therefore, the wafer 1W can be neatly cut.

FIG. 20 is a plan view of a whole chip 1C cut out from the semiconductorwafer 1W in the above-described manner. Here, the case is exemplarilyshown where the plurality of pads 1LB are arranged along only one sideat an end of the chip 1C in the longitudinal direction. In the firstembodiment, a part of the cutting region CR is left around the periphery(two sides crossing (orthogonal to) each other) of the chip 1C, and thetest pads 1LBt are left on that cutting region CR. Here, in the firstembodiment, after stealth dicing as described above, the jig 7 on whichthe plurality of ultrathin chips 1C are placed may be conveyed forshipping to another factory (an assembly fab, for example), to which arequest for assembling after dicing may be made.

Next, the procedure goes to the assembling step 102C. Here, the jig 7holding the plurality of chips 1C is carried to a pick-up device. By thepick-up device, with the back surface of the tape 7 a beingvacuum-sucked, the chip 1C is pressed up from the back surface of thetape 7 a by a press pin. At this time, when the UV tape as describedabove is used as the tape 7 a, an adhesive layer 7 a 2 of the tape 7 ais irradiated with ultraviolet rays so as to cure to weaken the adhesivelayer 7 a 2. In this state, the chip 1C is vacuum-absorbed with a colletto pick the chip 1C up (step 102C1).

Then, the above picked-up chip 1C is reversed by the existing reversingunit so that the main surface of the chip 1C faces up, and then the chip1C is mounted on a wiring board or the like (die bonding step 102C2).FIG. 21 is a plan view of the chips 1C and a wiring board 15 after thedie bonding step. FIG. 22 is a cross-sectional view taken along the lineX5-X5 of FIG. 21. On a main surface of the wiring board 15, for example,three chips 1C are mounted as being multilayered, with their mainsurfaces facing up. These three chips 1C are stacked as being shifted inplane so that the pads 1LB of the respective chips 1C are exposed.Although the wiring board 15 is formed of a printed wiring board, a leadframe may be used instead. Here, the picked-up chips 1C may beaccommodated in a carrier tray and be conveyed for shipping to anotherfactory (an assembly fab, for example), to which a request forassembling after this process may be made (process 103A).

Subsequently, the procedure goes to a wire bonding step (step 102C3).FIG. 23 is a plan view of the chips 1C and the wiring board 15 after thewire bonding step. FIG. 24 is a cross-sectional view taken along theline X6-X6 of FIG. 23. In this process, the pads 1LB on the mainsurfaces of the chips 1C and electrodes of the wiring board 15 areelectrically connected together through bonding wires (hereinaftersimply referred to as wires) 17. Here, as shown in FIG. 64, a pad 1LB onan upper chip 1C and a pad 1LB on a lower chip 1C are electricallyconnected together through a wire 17. That is, step bonding system maybe used, in which common pads are electrically connected together.

Subsequently, the procedure goes to a sealing step (step 102C4). FIG. 25is a cross-sectional view of the semiconductor device after the sealingstep. In this step, a transfer mold method is used to seal the chips 1Cand the wires 17 with a sealing member 18 made of a plastic material,such as epoxy resin. Then, bump electrodes 19 are formed on the backsurface of the wiring board 15 to manufacture the semiconductor device.

When the chip 1C has bump electrodes (protruded electrodes), theprocedure goes as follows, for example. First, in the pick-up step102C1, the chip 1C is moved to a chip mounting region on the wiringboard 15. At this time, the bump electrodes are connected to the pads1LB and the test pads 1LBt, thereby being mounted on the wiring board 15without a tilt of the chips. Subsequently, as making the main surfaces(bump-electrode formation surface) of the chip 1C facing the chipmounting surface of the wiring board 15, the bump electrodes of the chip1C and the electrodes of the chip mounting region are temporarily fixedto each other by using a paste material. After that, a reflow treatmentis performed, thereby temporarily fixing the bump electrodes of the chip1C and the electrodes of the printed wiring board 15 to each other(flip-chip bonding: step 102C2). After that, a space between the surfaceof the chip 1C and the surface of the wiring board 15 facing each otheris filled with an underfill, and then the chip 1C is sealed in a mannersimilar to that described above (step 104C4).

Second Embodiment

In a second embodiment, a modification example of an arrangement of thepads 1LB in the chip 1C will be described. FIG. 26 is a plan view ofwhole of a chip 1C according to the second embodiment. In the secondembodiment, the plurality of pads 1LB are arranged along two sidescrossing (orthogonal to) each other of the chip 1C. Other than that, thesecond embodiment is same with the first embodiment, where part of thecutting region CR is left around the periphery (two sides crossing(orthogonal to) each other) of the chip 1C, and the test pads 1LBt areleft on that cutting region CR.

FIG. 27 is a plan view of an example of mounting the chips 1C of FIG.26. A cross section taken along the line X7-X7 in FIG. 27 is identicalto that in FIG. 22 described above. On the main surface of the wiringboard 15, for example, three chips 1C are mounted as being multilayered,with their main surfaces facing up. These three chips 1C are stacked asbeing shifted in plane so that the plurality of pads 1LB arranged alongtwo sides of each chip 1C are exposed.

Third Embodiment

First, prior to descriptions of a third embodiment, a problem found forthe first time by the inventors of the present invention will bedescribed. As discussed above, in dividing the wafer 1W, there is aproblem that the beard-like conductive substance may occur at cuttingportions of the metal patterns, such as the test pads 1LBt existing inthe cutting region CR and the alignment target Am. To avoid thisproblem, the inventor formed grooves like perforations or straight lineson the metal patterns, such as the pads 1LBt and the alignment target Amon the cutting region CR. However, when the expansion method is adoptedas the dividing method, even if grooves like perforations or straightlines are formed on the metal patterns, the occurrence of a beard-likeconductive substance could not be sufficiently prevented. Moreover, at aportion having only an insulating film between adjacent metal patternson the cutting region CR, the cutting line meanders, thereby making itimpossible to neatly cut the wafer.

Accordingly, when the bending method is adopted in which the wafer 1W isbent to be divided into individual chips 1C, the occurrence of abeard-like conductive substance can be reduced compared with theexpansion method. However, even by the bending method, the cutting linemeanders between metal patterns. In particular, as described above, whena low-dielectric-constant film is used as the interlayer insulatingfilm, since the low-dielectric-constant film is brittle and tends to becracked, a crack is produced that meanders widely at the cutting portionbetween adjacent metal patterns, thereby making it impossible tosufficiently neatly cut the wafer. Consequently, the inventor tried toform a groove for a division starting point by irradiating a laser beamonto an interlayer-insulating-film portion between adjacent metalpatterns, and in the third embodiment, means for solving the aboveproblem will described. FIG. 28 is a plan view of main parts of a wafer1W according to the third embodiment. FIG. 29 is a cross-sectional viewtaken along the line X8-X8 of FIG. 28. FIG. 30 is a cross-sectional viewtaken along the line X9-X9 of FIG. 28.

The wafer 1W shown in FIGS. 28 to 30 is the wafer 1W after the front-endprocess 100 and the test process 101 and before the back-end process 102in FIG. 1. In the third embodiment, on the cutting lines CL in thecutting regions CR, metal patterns such as the test pads 1LBt and thealignment target Am are arranged. That is, the cutting lines CL overlapthe metal patterns such as the test pads 1LBt and the alignment targetAm. And, on the cutting lines CL, metal patterns 20 are formed so as tobury spaces between adjacent test pads 1LBt and spaces between the testpads 1LBt and the alignment target Am. However, the metal patterns 20 donot make contact with the metal patterns, such as the test pads 1LBt andthe alignment target Am, and are in an electrically floating state.Further, the metal patterns 20 are formed of the same material in thesame process as that of the test pads 1LBt and the alignment target Am.However, here, the width of each metal pattern 20 (short-directiondimension) is smaller than the length of one side of each test pad 1LBt,and is on the order of 5 to 10 μm, for example. Accordingly, materialcost can be reduced. Part of the upper surface of each metal pattern 20is exposed via an opening 5 formed in a protective film 1Lp.

Next, the back-surface processing step 102A is performed for thinning onsuch the wafer 1W in a manner similar to that according to the firstembodiment, and then the procedure goes to the chip dividing step 102B.In the chip dividing step, similarly to the first embodiment, after thepattern recognizing step 102B1 on the wafer main surface is performed,the procedure goes to a laser irradiation step 102B2. In the thirdembodiment, irradiation with a laser beam is performed twice.

Radiation with a laser beam of the first round forms a division startingpoint on the metal pattern in the cutting region CR. FIGS. 31 and 32 arecross-sectional views of main parts of the wafer 1W, showing the stateof irradiating a laser beam LB2 of the first round. FIG. 31 correspondsto a view taken along the line X8-X8 in FIG. 28, whilst FIG. 32corresponds to a view taken along the line X9-X9 in FIG. 28. In theirradiation with the laser beam of the first round, based on the patterninformation obtained by the IR camera, the cutting lines CL are aligned(corrected in position), and then the laser beam LB2 emitted from alaser generating unit is irradiated from the back surface side of thewafer 1W by placing a focal point at the test pads 1LBt, the alignmenttarget Am, and the metal patterns 20. Also, the laser beam LB2 is movedalong the cutting lines aligned based on the pattern information. Thecutting lines in the third embodiment overlap the test pads 1LBt, thealignment target Am, and the metal pattern 20 where a substantiallycenter of the cutting region CR in a width direction (short direction).Examples of radiation conditions of the laser beam LB2 are as follows.That is, a light source is a YAG laser at a wavelength of, for example,1064 nm and its radiation speed is 300 mm/s.

FIG. 33 is a plan view of main parts of the wafer 1W after thelaser-beam irradiation step with the laser beam LB2. FIGS. 34 and 35 arecross-sectional views taken along the line X10-X10 and the line X11-X11of FIG. 33. As irradiating the laser beam LB2 as described above, aplurality of holes 21 like perforations (broken lines or dots) in a planview are formed on the test pads 1LBt, the alignment target Am, and themetal patterns 20 along the cutting lines. These holes 21 serve asdivision starting points in the process of dividing (cutting) the wafer1W. That is, in the third embodiment, with the metal patterns 20 beingprovided between adjacent test pads 1LBt and between test pads 1LBt andthe alignment target Am, the arrangement of the plurality of holes 21serving as division starting points can also be formed between adjacenttest pads 1LBt and between test pads 1LBt and the alignment target Am.In irradiation with the laser beam LB2, molten substances may beattached to any test pad 1LBt or others. Therefore, in view ofsuppressing or preventing such molten substances from scattering, it isimportant to bring the tape 7 a into intimate contact with asperities ofthe cutting region CR.

Irradiation with a laser beam of the second round forms the modifiedregion PR described in the first embodiment. FIGS. 36 and 37 arecross-sectional views of main parts of the wafer 1W, showing the stateof irradiating the laser beam LB1 for the second time. FIG. 36corresponds to the view taken along the line X8-X8 in FIG. 28, whilstFIG. 37 corresponds to the view taken along the line X9-X9 in FIG. 28.Here, as with the first embodiment described above, the laser beam LB1is irradiated from the back surface side of the wafer 1W by placing afocal point in the inside of the substrate 1S. In this manner, themodified region PR in the substrate 1S formed. However, in the thirdembodiment, the laser beam LB1 is irradiated at the center of thecutting region CR in the width direction (short direction). That is, theoperation path of the unit for generating the laser beam LB1 isidentical to the operation path of the unit for generating the laserbeam LB2. However, as described in the first embodiment, the shape ofthe modified region PR may be straight lines or broken lines in a planeview. When the laser beam LB1 and LB2 are irradiated from the same backsurface side of the wafer 1W, after the laser beam LB2 is firstirradiated, and the laser beam LB1 is irradiated. This is because, ifthe laser beam LB1 is first irradiated before the laser beam LB2, themodified region PR formed in the substrate 1S by irradiating the laserbeam LB1 may cause an obstruction at the time of irradiating the laserbeam LB2, thereby making it impossible to form the holes 21 on the metalpatterns on the cutting region CR.

Next, in the dividing step 102B3, as with the first embodiment, thewafer 1W is divided (cut) by bending the wafer 1W. FIG. 38 is a planview of the whole chip cut out from the wafer 1W. FIG. 39 is across-sectional view taken along the line X12-X12 of FIG. 38. In thethird embodiment, the wafer 1W can be neatly cut along the arrangementof the holes 21. That is, even when a low-dielectric-constant film isused as the interlayer insulating film, the wafer 1W can be divided(cut) along the arrangement of the plurality of holes 21 withoutmeanders even between adjacent test pads 1LBt and between test pads 1LBtand the alignment target Am. Therefore, defects in cut-out shape of thewafer 1W can be reduced or prevented, thereby increasing yield andreliability of a semiconductor device. Note that, parts of the test pads1LB, the alignment target Am, and the metal patterns 20 are left aroundthe outer periphery of the chip 1C. Also, the assembling process 102C isidentical to that in the first embodiment, and therefore is notdescribed herein.

Fourth Embodiment

In the first to third embodiments, since the test pads 1LBt and the TEGelements are left on the outer periphery of the chips 1C, TEGinformation may disadvantageously leak out to the outside. In a fourthembodiment, means for avoiding such a problem will be described. In thefollowing, an example of a method of manufacturing a semiconductordevice according to the fourth embodiment will be described according toa flow of FIG. 40 also with reference to FIGS. 41 to 50.

First, as with the first embodiment, after a front-end process 200 and atest process 201, the procedure goes to a back-end process 202. In aback-surface processing step 202A of the back-end process 202, asupporting substrate is adhered on the main surface of the wafer 1W viaan adhesive layer (step 202A1). FIG. 41 is a cross-sectional view of thewafer 1W after a supporting substrate 24 is attached.

This supporting substrate 24 is a Wafer Support System (WSS) thatfunctions as a reinforcing member for the wafer 1W in subsequent steps.Accordingly, at the time of carrying the wafer 1W, the ultrathin wafer1W with a large diameter can be handled in a stable state. Furthermore,the wafer 1W can be protected against an impact from outside, therebysuppressing or preventing cracks, chipping, or others of wafer 1W. Also,at each steps thereafter, warpage and distortion of the wafer 1W can besuppressed or prevented, thereby improving flatness of the ultrathinwafer 1W with a large diameter. Therefore, stability and controllabilityof each step can be improved.

The supporting substrate 24 is made by using, for example, a hardsupporting substrate (Hard-WSS or Glass-WSS), such as transparent glass.However, another hard supporting substrate (Hard-WSS), such asstainless, may be used for the supporting substrate 24. Also, stillanother material may be used for the supporting substrate 24. Forexample, a tape WSS with an insulating supporting substrate made of PET(Polyethylene Terephthalate) or PEN (Polyethylene Naphthalate) beingadhered to a tape base material may be used.

Here, to adhere the supporting substrate 24 onto the main surface of thewafer 1W, a surface of the supporting substrate 24 on which a peelinglayer 24 a is formed is pressed onto an adhesive layer 25 on the mainsurface side of the wafer 1W, thereby fixing the supporting substrate 24to the main surface of the wafer 1W. This peeling layer 24 a is afunctional layer for facilitating peeling-off when the supportingsubstrate 24 is peeled off from the wafer 1W. In place of the supportingsubstrate, a so-called BG tape may be used.

Next, as with the first embodiment, after the thickness of the wafer 1Wis measured, based on the measurement results, a grinding process and apolishing process (planarizing process) are performed in sequence on theback surface of the wafer 1W (steps 202A2 and 202A3). FIG. 42 is across-sectional view of the wafer 1W after such thinning processes. Abroken line of FIG. 42 denotes the substrate 1S before the thinningprocesses.

Subsequently, the procedure goes to a chip dividing step 202B. A laserirradiation step 202B2 of the chip dividing step 202B forms the modifiedregion PR described in the first embodiment. FIG. 43 is across-sectional view of main parts of the wafer 1W, showing a state ofirradiating the laser beam LB1.

Also in the fourth embodiment, as with the first embodiment, the laserbeam LB1 is irradiated from the back surface side of the wafer 1W byplacing a focal point in the inside of the substrate 1S to form themodified region PR in the substrate 1S. However, in the fourthembodiment, the laser beam is irradiated to both sides of the metalpatterns, such as the test pads 1LBt and at a plane positioncorresponding to a boundary or space between the chip 1C and the cuttingregion CR. The shape of the modified region PR may be straight lines orbroken lines in a plane view, as described in the first embodiment.

After that, in a wafer mounting step 202B2, the wafer 1W is re-adheredto a jig. FIG. 44 is a plan view of the wafer 1W and the jig 7 after thewafer mounting step 202B2 and a WSS peeling-off step 202B3. FIG. 45 is across-sectional view taken along the line X13-X13 of FIG. 44.

In the wafer mounting process 202B2, with the supporting substrate 24being adhered to the main surface (device formation surface) of thewafer 1W, the back surface of the wafer 1W is adhered to a tape 7 a ofthe jig 7. The wafer 1W is firmly fixed to an adhesive layer 7 a 2 ofthe tape 7 a. With this, the wafer 1W is accommodated in the jig 7 withits main surface on the front and being exposed.

Then, in the WSS peeling-off process 202B3, laser beam is irradiatedacross the main surface of the wafer 1W for scanning via the transparentsupporting substrate 24 by placing a focal point at the adhesive layer25 on the main surface of the wafer 1W. With this, after the supportingsubstrate 24 is peeled off from the wafer 1W, the adhesive layer 25 onthe main surface of the wafer 1W is removed. Laser light conditions inthis process are such that, for example, an infrared laser has awavelength of 1064 nm, an output of 20 W, a radiation speed of 2000mm/s, a spot diameter on the order of f200 μm. When the adhesive layeris formed of ultraviolet cure resin (UV resin), an ultraviolet laser isused in place of an infrared laser. With this, the adhesiveness of theadhesive layer 25 can be weakened, thereby making it easy to peel offthe supporting substrate 24.

Next, in the fourth embodiment, the procedure goes to a TEG processingstep 202B4. In the TEG processing step 202B4, the jig 7 having the wafer1W accommodating thereon is placed on a dicing stage of a dicingapparatus to remove TEG by a rotating dicing saw (blade dicing). FIG. 46is a cross-sectional view of main parts of the wafer 1W during this TEGprocessing step. Here, a dicing saw 26 for use has a rectangular crosssection. After aligned with the cutting region CR, this dicing saw 26 isrotated and goes down so as to make contact with the main surface of thewafer 1W. With this, the metal patterns, such as the TEG test pads 1LBtand the alignment target Am, are removed. FIG. 47 is a cross-sectionalview of main parts of the wafer 1W after the TEG processing step. Here,the metal patterns, such as the TEG test pads 1LBt, on the cuttingregion CR are completely removed, and a groove 27 is formed in thecutting region CR on the main surface of the wafer 1W. The groove 27 hasa depth at some midpoint of the wiring layer 1L, but may reach thesubstrate 1S, provided that the substrate 1S is never completely cutoff.

Then, in the dividing step 202B5, as with the first embodiment, thewafer 1W is divided (cut) through a bending method. FIG. 48 is anenlarged cross-sectional view of main parts of the wafer 1W during thedividing step 202B5. In this case, in general, of two modified regionsPR in the cutting region CR, a crack occurs on either one of theseregions that has a weak mechanical strength, thereby cutting the wafer1W. In the fourth embodiment, since the metal patterns, such as the testpads 1LBt and the alignment target Am, are removed, no beard-likeconductive substance occurs.

FIG. 49 is a plan view of a whole chip 1C cut out from the wafer 1W.FIG. 50 is a cross-sectional view taken along the line X14-X14 of FIG.49. In the fourth embodiment, since no metal patterns, such as the testpads 1LBt and the alignment target Am, are left on the periphery of thechip 1C, it is possible to prevent leakage of TEG information.

An assembling process 202C (202C1 to 202C4, 203A) thereafter isidentical to the assembling process 102C (102C1 to 102C4, 103A)according to the first embodiment, and are therefore not describedherein.

Fifth Embodiment

Although leakage of TEG information can be prevented in the fourthembodiment, the cutting lines described in the third embodimentdisadvantageously meander. In a fifth embodiment, a means for avoidingthis problem is described.

First, as with the fourth embodiment, after the front-end process 200,the test process 201, and the back-surface processing step 202A of theback-end process 202, the procedure goes to a laser irradiation step202B1 of the chip dividing step 202B. FIG. 51 is a cross-sectional viewof main parts of the wafer 1W during the laser irradiation stepaccording to the fifth embodiment. Here, as with the first to fourthembodiments, the laser beam LB1 is irradiated from the back surface ofthe wafer 1W by placing a focal point at the inside of the substrate 1Sto form the modified region PR on the substrate 1S. However, in thefifth embodiment, the laser beam LB1 is irradiated at the center of thecutting region CR in the width direction (short direction). That is, thelaser beam LB1 is irradiated at a position that overlaps the metalpatterns, such as the test pads 1LBt and the alignment target Am, in aplane. As described in the first embodiment, the shape of the modifiedregion PR may be straight lines or broken lines in a plane view.

Then, as with the fourth embodiment, after the wafer mounting process202B2 and the WSS peeling-off processing step 202B3, the procedure goesto a TEG processing step 202B4. FIG. 52 is a cross-sectional view ofmain parts of the wafer 1W during the TEG processing step 202B4. In thisTEG processing step, as with the fourth embodiment, the rotating dicingsaw 26 is put on the cutting region CR on the main surface of the wafer1W to remove the metal patterns, such as the test pads 1LBt and thealignment target Am. However, in the fifth embodiment, as the dicing saw26, the one having a wedge shape (V shape) in cross section at the tipof its outer periphery is used.

FIG. 53 is a plan view of main parts of the wafer 1W after the TEGprocessing step. FIG. 54 is a cross-sectional view taken along the lineX15-X15 of FIG. 53. Here, the metal patterns, such as the test pads 1LBtand the alignment target Am, are completely removed, and a groove 27 isformed in an upper surface of the interlayer insulating film 1Li (wiringlayer 1L) of the cutting region CR on the main surface of the wafer 1W.The groove 27 has the same depth as that in the fourth embodiment.However, in the fifth embodiment, as the groove 27 goes deeper, thewidth becomes narrower. That is, the groove 27 has a V shape in crosssection. The deepest portion of the groove 27 functions as a divisionstarting point for the interlayer insulating film 1Li at the time of thedividing step 202B5. The groove 27 is formed so that the portionfunctioning as a division starting point is positioned in a plane viewat the center of the cutting region CR in the width direction (shortdirection), that is, so that the portion coincides with a plane positionof the modified region PR (that is, the cutting line CL).

Then, in a dividing step 202B5, as with the first embodiment, the wafer1W is divided (cut) through a bending method. FIG. 55 is an enlargedcross-sectional view of main parts of the wafer 1W during a dividingstep 202B5. In this case, the wafer 1W is divided (cut) with themodified region PR and the groove 27 on the wiring layer 1L on thesubstrate 1S as dividing starting points.

In the fifth embodiment, since the metal patterns, such as the test pads1LBt and the alignment target Am, are removed, a beard-like conductivesubstance does not occur. Also, with the V shape in cross section of thegroove 27, even when a low-dielectric-constant film is used as aninterlayer insulating film, the wafer 1W (in particular, the interlayerinsulating film 1Li on the main surface side of the wafer 1W) can beneatly divided (cut) along the groove 27 without meandering. Therefore,yield and reliability of a semiconductor device can be increased.

FIG. 56 is a plan view of a whole chip 1C cut out from the wafer 1W.FIG. 57 is a cross-sectional view taken along the line X16-X16 of FIG.56. In the fifth embodiment, since the metal patterns, such as the testpads 1LBt and the alignment target Am, are not left around the peripheryof the chip 1C, the leakage of TEG information can be prevented. Also,in the fifth embodiment, the periphery angle on the main surface side ofthe chip 1C is tilted. That is, a taper is formed at the periphery angleon the main surface of the chip 1C. With this, chipping of the peripheryangle of the chip 1C can be reduced, for example, at the time ofcarrying the chip 1C. Therefore, yield and reliability of asemiconductor device can be increased. Also, the occurrence of foreignsubstances can be reduced.

An assembling process 202C (202C1 to 202C4, 203A) thereafter isidentical to the assembling process 102C (102C1 to 102C4, 103A)according to the first embodiment, and are therefore not describedherein.

Sixth Embodiment

In a sixth embodiment, an example of a method of removing TEG with laserbeam to prevent the leakage of TEG information is described.

First, as with the fifth embodiment, after the front-end process 200 tothe WSS peeling-off process 203B3, TEG is removed with laser beam in aTEG processing step 202B4. FIG. 58 is a cross-sectional view of mainparts of the wafer 1W during the TEG processing step. Laser light(second laser) LB3 is irradiated from the main surface side of the wafer1W to the metal patterns, such as the test pads 1LBt and the alignmenttarget Am, thereby melting these metal patterns for removal. As thelaser beam LB3, laser beam having a shorter wavelength than thewavelength of the laser beam LB1 at the time of forming the modifiedregion PR is used, such as a ultraviolet ray having a wavelength of, forexample, 355 nm. By irradiating the laser beam LB3 to each metal patternfor a plurality of number of times, these metal patterns are removed.FIG. 59 is a cross-sectional view of main parts of the wafer 1W afterthe TEG processing step in the sixth embodiment. Here, the metalpatterns, such as the test pads 1LBt, on the cutting region CR arecompletely removed. In the sixth embodiment, with the metal patterns onthe cutting region CR being removed with the laser beam LB3, the metalpatterns can be removed without applying a mechanical stress to thewafer 1W, thereby preventing the occurrence of damage, such as chipping,around the periphery of the chip 1C. With this, the bending strength ofthe thin semiconductor chip can be increased compared with those in thefourth and fifth embodiments.

Then, in a dividing step 202B5, as with the first embodiment, the wafer1W is divided (cut) through a bending method. FIG. 60 is an enlargedcross-sectional view of main parts of the wafer 1W during the dividingstep 202B5. In this case, the wafer 1W is divided (cut) with themodified region PR on the substrate 1S as a dividing starting point. Inthe fifth embodiment, since the metal patterns, such as the test pads1LBt and the alignment target Am, are removed, a beard-like conductivesubstance does not occur.

A plan view of the whole chip 1C cut out from the wafer 1W in the sixthembodiment is similar to the plan view of FIG. 49. Also in the sixthembodiment, the metal patterns, such as the test pad 1LBt or thealignment target Am, do not remain around the periphery of the chip 1C.Therefore, the leakage of TEG information can be prevented.

An assembling process 202C (202C1 to 202C4, 203A) thereafter isidentical to the assembling process 102C (102C1 to 102C4, 103A)according to the first embodiment, and are therefore not describedherein.

Seventh Embodiment

Although the leakage of TEG information can be prevented in the sixthembodiment, the cutting lines described in the third embodimentdisadvantageously meander. In a seventh embodiment, a means for avoidingthis problem is described.

First, as with the fifth and sixth embodiments, after the front-endprocess 200 to the WSS peeling-off process 203B3, the procedure goes toa TEG processing step 202B4. In this TEG processing step 202B4, laserbeam is irradiated to TEG. FIG. 61 is a cross-sectional view of mainparts of the wafer 1W during the TEG processing step 202B4. FIG. 63 isan enlarged cross-sectional view of main parts of the wafer 1W duringthe TEG processing step 202B4. Here, as with the sixth embodiment, thelaser beam LB3 is irradiated from the main surface side of the wafer 1Wto the metal patterns, such as the test pad 1LBt or the alignment targetAm to form a groove 30 in a part of the metal patterns on an uppersurface of the metal pattern, such as the test pads 1LBt and thealignment target Am, on the cutting region CR. The groove 30 is formedthrough melting with heat of the laser beam LB3, and the molten portiondevelops to an interface of the interlayer insulating film 1L2 (wiringlayer 1L). As a result, a crack CRK is formed from the groove 30 to themodified region PR. The groove 30 is formed so as to be positioned in aplan view at the center of the cutting region CR in the width direction(short direction), that is, so as to coincide with a plane position ofthe modified region PR (that is, the cutting lines CL). Here, in theseventh embodiment, since only part of the metal patterns on the cuttingregion CR are removed, damage, such as chipping, does not occur aroundthe periphery of the chip 1C even with this laser-light processing. Withthis, the bending strength of the thin semiconductor chip can beincreased compared with the fourth and fifth embodiments.

Then, in a dividing step 202B5, as with the first embodiment, the wafer1W is divided (cut) through a bending method. FIG. 62 is an enlargedcross-sectional view of main parts of the wafer 1W during a dividingstep 202B5. In this case, the wafer 1W is divided (cut) with themodified region PR in the substrate 1S, the crack CRK, and the groove 30in the wiring layer 1L as division starting points.

In the seventh embodiment, since a cut-off portion of the metalpatterns, such as the test pads 1LBt and the alignment target Am,(groove 30 formation portion) is cut off, no beard-like conductivesubstance occurs. Also, since the groove 30 reaches the interlayerinsulating film 1Li, even when a low-dielectric-constant film is used asan interlayer insulating film, the wafer 1W (in particular, theinterlayer insulating film 1Li on the main surface side of the wafer 1W)can be neatly divided (cut) along the groove 30 without meandering.Therefore, yield and reliability of a semiconductor device can beincreased.

The chip 1C cut out from the wafer 1W in the seventh embodiment issubstantially identical to those in FIGS. 56 and 57. Also in the seventhembodiment, part of the metal patterns, such as the test pad 1LBt or thealignment target Am, remain around the periphery of the chip 1C, but arecut off and melted, thereby making it impossible to obtain the TEGinformation. Therefore, the leakage of TEG information can be prevented.Also, in the seventh embodiment, with the periphery angle on the mainsurface side of the chip 1C being tilted by the formation of the groove30, chipping of the periphery angle of the chip 1C can be reduced at thetime of carrying the chip 1C or the like. Therefore, yield andreliability of a semiconductor device can be increased. Furthermore, theoccurrence of foreign substances can be reduced.

An assembling process 202C (202C1 to 202C4, 203A) thereafter isidentical to the assembling process 102C (102C1 to 102C4, 103A)according to the first embodiment, and is therefore not describedherein.

Eighth Embodiment

In the fourth and fifth embodiments, a dicing saw 26 is used to removeTEG (blade dicing), thereby preventing the leakage of TEG informationand a defect in mounting due to a beard-like conductive foreignsubstance (hair defect) of TEG. However, with demands for furtherreduction in thickness of semiconductor devices, when the thickness ofthe wafer 1W becomes thin as much as 70 μm or smaller, for example, asshown in FIG. 66, a problem of a chip crack tends to occur. This isbecause the dicing saw 26 is used for removing TEG, a distance (space)from the fractured layer (modified region PR) to TEG is closer (shorter)as the wafer 1W becomes thinner, and the bending strength of the wafer1W (chips 1C) is decreased. In blade dicing, the dicing saw 26 rotatingat high speed is brought into contact with the wafer 1W to cut (rupture)the wafer 1W. Therefore, the cutting stress (rupture stress) exerted onthe wafer 1W is larger than that in stealth dicing. That is, asdescribed in the fourth and fifth embodiments, when laser beam isirradiated in advance to the wafer 1W to form a fractured layer(modified region PR) and then TEG is removed by using the dicing saw 26,the distance (space) from the fractured layer to TEG is short.Furthermore, since the bending strength of the wafer 1W is decreased,the cutting stress of the dicing saw 26 tends to develop to thefractured layer, thereby causing a crack CRK. In an eighth embodiment, ameans for avoiding this problem is described.

First, as shown in FIG. 67, the dicing saw 26 is used to remove the testpads 1LBt and the alignment target Am arranged on the cutting region onthe main surface of the wafer 1W. With this, a groove 27 is formed onthe main surface of the wafer 1W.

Next, as shown in FIG. 68, a BG tape 35 is adhered to the main surfaceof the wafer 1W. A tape base 35 a of the BG tape 35 is made of a plasticmaterial with plasticity, for example, and has its main surface on whichan adhesive layer 35 b is formed. The BG tape 35 is firmly adhered tothe main surface (chip formation surface) of the wafer 1W with thisadhesive layer 35 b.

Then, after reversing the wafer 1W, as shown in FIG. 69, thegrinding/polishing tool (grindstone) 8 described above is used from theback surface side of the wafer 1W to perform a back-surface grindingprocess, and further to perform a polishing process (stress relief) inorder to remove minute asperities formed on the back surface of thewafer 1W through the back-surface grinding process, thereby making adesired thickness of the wafer 1W.

Next, as shown in FIG. 70, the laser beam LB1 is irradiated from theback surface of the wafer 1W to form the modified region (opticallydamaged parts or fractured layer) PR inside (near the center in thethickness direction) of the wafer 1W in a manner similar to the above.

Next, as shown in FIG. 71, the tape 7 a of the jig 7 is adhered to theback surface of the wafer 1W. Then, after reversal, the BG tape 35 ispeeled off from the main surface of the wafer 1W (wafer mountingprocess). Then, as shown in FIG. 72, an expansion method is used tofragment the wafer 1W, thereby obtaining the plurality of chips 1C.

In this manner, according to the eighth embodiment, each of the testpads 1LBt and the alignment target Am is removed in advance by thedicing saw 26 before the back-surface grinding process for making thewafer 1W thinner and the process of forming the modified region PR.Therefore, even when the wafer 1W is thinner as small as 70 μm orsmaller, for example, the problem of a chip crack can be suppressed.

Here, when the dicing saw 26 is used to remove TEG after the fracturedlayer (modified region PR) is formed, the problem of a chip crack occursdue to the cutting stress of the dicing saw 26. Only in view of this, away can be thought in which the dicing saw 26 is used to remove TEG fromthe main surface side of the wafer W1 and then the laser beam LB1 isirradiated again from the main surface side of the wafer 1W to form afractured layer (modified region PR) on the wafer 1W.

However, as shown in FIG. 73, minute asperities are formed on thesurface of the wafer (that is, a bottom surface of the groove 27) cutdown by the dicing saw 26. Therefore, when the laser beam LB1 isirradiated, diffusion occurs, thereby making it difficult to place afocal point of the laser beam LB1 at the inside of the wafer 1W.

Also, another way can be thought in which, after the dicing saw 26 isused to remove TEG, the wafer 1W is reversed, and then laser beam isirradiated from the back surface side of the wafer 1W to form afractured layer (modified region PR), and then a back-surface grindingprocess and a polishing process for making the wafer 1W thinner areperformed.

However, if the fractured layer (modified region PR) is formed inadvance on the wafer 1W before the back-surface grinding process and thepolishing process, a crack CRK may occur from the back surface of thewafer 1W to the fractured layer (modified region PR) due to the stressof the grindstone for back-surface grinding. For this reason, as in theeighth embodiment, after TEG is removed by the dicing saw 26, the wafer1W is made thinner through the back-surface grinding process and thepolishing process so as to have a desired thickness, and then the laserbeam LB1 is irradiated from the back surface side of the wafer 1W toform a fractured layer (modified region PR). Such a means is effectiveto address the problem of a chip crack.

Ninth Embodiment

When a semiconductor wafer is divided through blade dicing, the cuttingregion has to have a width wider than the width of the dicing saw foruse. By contrast, in stealth dicing, a fractured layer (modified regionPR) is formed inside of a semiconductor wafer, and then thesemiconductor wafer is divided with the fractured layer as a startingpoint. Therefore, compared with blade dicing, the width of the cuttingregion can be narrower.

However, on the cutting region CR, the test pads 1LBt and the alignmenttarget Am are arranged. Therefore, the cutting region CR has to have atleast a width wider than the widths of the test pads 1LBt and thealignment target Am. For this reason, it is difficult to increase thenumber of chips to be obtained from one wafer. To get around thisproblem, in a ninth embodiment, an example of a method for increasingthe number of chips to be obtained from one wafer is described withreference to FIGS. 74, 75, and 76. FIG. 74 is a plan view of a wafer 1Waccording to the ninth embodiment. FIG. 75 is an enlarged plan view ofmain parts of the main surface of the wafer 1W of FIG. 74. FIG. 76 is across-sectional view of main parts when TEG is removed from the wafer 1Wof FIG. 75.

First, as shown in FIGS. 74 and 75, on the main surface of the wafer 1W,of cutting regions CR (CR1 and CR2) provided in an X direction and a Ydirection (a direction crossing the X direction), the test pads 1LBt andthe alignment target Am are arranged only on the cutting region (firstcutting region) CR1 provided in the X direction. That is, on the cuttingregion (second cutting region) CR2 provided in the Y direction, the testpads 1LBt and the alignment target Am are not arranged at all, whilstthe test pads 1LBt and the alignment target Am are centrally arrangedonly on the cutting region CR1 provided in the X direction. With this,the width of the cutting region CR2 extending in the Y direction can benarrower than the widths of the test pads 1LBt and the alignment targetAm. Thus, the space between adjacent chips 1C (chip region) can benarrower, thereby increasing the number of chips 1C to be obtained fromone wafer 1W. Here, the width of the cutting region CR2 extending in theY direction is 5 μm, for example.

However, when the test pads 1LBt and the alignment target Am arecentrally arranged on the cutting region CR1 extending in the Xdirection, as shown in FIG. 75, a plurality of (two in the ninthEmbodiment) rows of test pads 1LBt and an alignment target Am arearranged in the cutting region CR1 extending in the X direction.Therefore, when the dicing saw having substantially the same width asthe width of TEG is used as in the fourth, fifth, and eighthembodiments, the dicing saw has to run twice with respect to one cuttingregion CR in order to completely remove TEG. Thus, it takes time toperform a TEG removing process.

To address this, in the ninth embodiment, as shown in FIG. 76, in aTEG-pattern removing process, the dicing saw 26 preferably has a widthsubstantially the same as the total width of these two TEGs. With this,even if the plurality of rows of TEG are arranged in the cutting regionCR2, all TEGs in the cutting region CR2 can be removed by running thedicing saw 26 only once. Here, although it has been described that thedicing saw 26 has a width substantially the same as the total width oftwo TEGs, it is preferable to completely remove all TEGs in the cuttingregions CR2 by running the dicing saw 26 at least once, and thereforethe width of the dicing saw 26 is preferably equal to or larger than thetotal width of two TEGs and also smaller than the width of the cuttingregion CR2.

In the ninth embodiment, the dicing saw 26 is moved only in onedirection to remove the TEG pattern, thereby shortening the time forremoving the TEG pattern. Here, a plurality of dicing saws 26 with awide width described in the ninth embodiment can be concurrentlyoperated at the same time, thereby further shortening the time forremoving the TEG pattern.

Tenth Embodiment

With the downsizing of a semiconductor device, further downsizing of achip is demanded. When stealth dicing also capable of thinning a waferis used as a downsized-chip dividing method, dividing one wafer intoindividual chips can be achieved by irradiating laser beam to the waferand then performing an expand process.

However, for example, when a chip having a width (length) of one sidebeing equal to or smaller than 3 mm is to be formed, as shown in FIG. 72in the eighth embodiment, if the whole dicing tape is tried to beexpanded through one expand process from the center to the periphery, aproblem of a defect in division tends to occur, in which adjacent onesof a plurality of chips 1C (chip regions) are not completely divided.This is because, when the size of each chip is small, a tension isdifficult to be transferred to each of the plurality of chip regionseven when the dicing tape is expanded, thereby causing a plurality ofchips to be connected. In a tenth embodiment, a means for avoiding thisproblem is described.

One wafer 1W is provided with a plurality of cutting regions CR so thatthese regions extend in the X direction and the Y direction. In thetenth embodiment, all of the plurality of cutting regions CR are notdivided through one expand process, but one of the plurality of cuttingregions CR is divided through one expand process.

This is described by using a plan view of the wafer 1W of FIG. 77. Thatis, as shown in FIG. 72, in an expand process for the first time, acutting region (first cutting region) CR indicated by “a” is firstdivided. Then, after diving the “a” cutting region, a cutting region(second cutting region) CR indicated by “b” is divided through an expandprocess for the second time. Then, an expand process is repeated untilall cutting regions CR are divided in the order of “c”, “d”, “e”, “f”cutting regions CR. With this, even when the width (length) of one sideof each chip 1C is small, by using the means in the tenth embodiment,the tension of the dicing tape can be reliably transferred to eachcutting region CR (cutting region CR for one line). Therefore, theproblem of a defect in division can be suppressed. Here, since theplurality of cutting regions CR are provided on the wafer 1W so as toextend in the X direction and the Y direction, for simplification of adividing mechanism, it is preferable to first divide the plurality ofall cutting regions CR provided so as to extend toward the X direction,and then divide the plurality of the cutting regions CR provided so asto extend toward the Y direction in this sequence.

Next, the dividing method according to the tenth embodiment is morespecifically described by using FIGS. 78 and 79.

FIG. 78A is a plan view of the whole wafer 1W, showing a specific stateof the process of dividing the wafer 1W described with reference to FIG.77. FIG. 78B is a cross-sectional view taken along the line X17-X17 ofFIG. 78A. FIGS. 79A and 79B are enlarged cross-sectional views of mainparts of the wafer 1W when the dividing step is performed.

As shown in FIG. 78, the wafer 1W adhered to the tape 7 a of the jig 7for dicing is placed on a stage of a stealth dicing apparatus. On thisstage, two tensile bars 40 extending across the wafer 1W along a Ydirection in FIG. 78A are placed in parallel so as to be adjacent toeach other in a plane view. Each tensile bar 40 has a widthsubstantially the same as the width of chips 1C on the wafer 1W in the Xdirection in FIG. 78A. Also, each tensile bar 40 is provided with avacuum absorption hole 41 as shown in FIG. 79. With this, the tensilebar 40 can be firmly adhered to the wafer 1W via the tape 7 a of the jig7 for dicing, and also the wafer 1W can be fixed.

First, for division by targeting only one cutting region CR (cuttingregion CR of one line), as shown in FIGS. 78 and 79, the wafer 1W isaligned so that the cutting region CR of one line on the wafer 1Woverlaps a space (cutting groove) between adjacent two tensile bars 40in a plan view. Then, these two tensile bars 40 are adhered to the wafer1W through vacuum absorption. That is, two tensile bars 40 are arrangedand fixed on both sides of a division region (cutting region CR for oneline) as a boundary.

Then, with the wafer 1W being vacuum absorbed by two tensile bars 40,two tensile bars 40 are moved in a direction so as to be away from eachother, as represented by arrows PA and PB in FIGS. 78 and 79 (indirections along the main surface of the wafer 1W). That is, two tensilebars 40 are moved in a direction so as to be drawn away from each otherto the outside from the space. With this, as shown in FIG. 79B, thewafer W1 fixed to the tensile bars 40 is divided, with (the modifiedregion PR of) the cutting region as a starting point.

When division of one cutting region CR (cutting region CR for one line)is completed, the wafer 1W is moved so that the cutting region CRdesired to be divided next overlaps a space between two tensile bars 40in a plan view. Then, the wafer 1W is divided in the above-describedmanner. By repeating the above operation until all cutting regions CRfor the plurality of lines are divided, the plurality of chips 1C can beobtained without causing a defect in division.

Here, in the tenth embodiment, the case has been described in which twotensile bars 40 are taken as one set. This is not meant to berestrictive, and the number of tensile bars 40 to be arranged may be asmany as the number of cutting regions CR for the plurality of lines onthe wafer 1W. With this, a process of shifting the wafer 1W every timeone expand process is over can be eliminated. FIGS. 80A to 80C show suchan example. CL1 represents a first division position, CL2 represents asecond division position, and CL3 represents a third division position.With each of the division positions CL1, CL2, and CL3 as a boundary, thetensile bars 40 on both sides are moved in a direction so as to be awayfrom each other (in directions represented by arrows PA and PB), therebydividing the wafer 1W in the above-described manner.

In the foregoing, the invention made by the inventors of the presentinvention has been concretely described based on the embodiments.However, it is needless to say that the present invention is not limitedto the foregoing embodiments and various modifications and alterationscan be made within the scope of the present invention.

For example, although the test pad 1LBt is shaped in a square in a planview in the first embodiment, this is not meant to be restrictive, andthe shape can be variously modified. For example, the test pad 1LBt maybe shaped in a rectangle (the length in a direction in which the cuttingregion CR extends (longitudinal direction) is longer than the length ina width direction of the cutting region CR) in a plan view. With this,the area of the pad 1LBt can be ensured to be large without so muchincrease of the width of the cutting region CR. That is, withsuppression of an increase in area of the chip 1C, the probe can bereliably placed onto the test pad 1LBt.

Also, in the third embodiment, the laser beam LB2 is irradiated from theback surface of the wafer 1W to form the holes 21 on the metal patternsin the cutting regions CR on the main surface of the wafer 1W.Alternatively, as described with reference to the flow of FIG. 40, whenthe wafer mounting process is performed, the laser beam LB2 can beirradiated from the main surface of the wafer 1W. In this case, aprocess of irradiating the laser beam LB2 can be performed in place ofthe TEG processing step 202B4 in FIG. 40. That is, by irradiating thelaser beam LB2 from the main surface side of the wafer 1W to the testpads 1LBt, the alignment target Am, and the metal patterns 20 on thecutting region CR on the main surface of the wafer 1W, the holes 21 areformed in the test pads 1LBt, the alignment target Am, and the metalpatterns 20. In this case, in place of the holes 21, grooves may beformed in the test pads 1LBt, the alignment target Am, and the metalpatterns 20. The shape of these grooves may be a straight line or abroken line in a plane view. The other processes are same to thosedescribed in the first to seventh embodiments.

Although the cases has been described in the foregoing descriptions inwhich the invention devised by the inventors of the present invention isapplied to a method of manufacturing a semiconductor device which is thebackground field of the invention, the invention is not limited to this,and various modifications can be applied to the invention. For example,the present invention can be applied to a micromachine manufacturingmethod.

INDUSTRIAL APPLICABILITY

The present invention can be applied to manufacturing industries forproducts with a process of dividing a wafer through stealth dicing.

1. A method of manufacturing a semiconductor device, comprising thesteps of: (a) providing a semiconductor wafer having a substrateincluding a front surface, an interlayer insulating film formed on thefront surface of the substrate, a first chip region formed over thefront surface of the substrate, a second chip region formed over thefront surface of the substrate and arranged next to the first chipregion, a cutting region formed over the front surface of the substrateand formed between the first chip region and the second chip region in aplan view, a metal pattern formed over the front surface of thesubstrate and formed in the cutting region in the plan view and arrangedbetween the first chip region and the second chip region in the planview, and a back surface opposite to the front surface, wherein theinterlayer insulating film has a wiring layer and a low-dielectricconstant film, wherein the substrate is comprised of a silicon, andwherein the low-dielectric constant film is more brittle than thesubstrate; (b) after the step (a), removing the metal pattern by runninga dicing saw along the cutting region; (c) after the step (b), attachinga back grind (BG) tape to the front surface of the semiconductor wafer,and grinding the back surface of the semiconductor wafer; (d) after thestep (c), forming a modified region in the cutting region of thesemiconductor wafer by irradiating along the cutting region with alaser; and (e) after the step (d), attaching a dicing tape to the backsurface of the semiconductor wafer, and removing the back grind (BG)tape from the semiconductor wafer; (f) after the step (e), separatingthe first chip region from the second chip region by expanding thedicing tape attached to the back surface of the semiconductor wafer. 2.The method according to claim 1, wherein in the step (b), the metalpattern and a portion of the interlayer insulating film are removed byrunning the dicing saw.
 3. The method according to claim 1, wherein thelow-dielectric constant film is comprised of one of an organic polymerand organic silica glass.
 4. The method according to claim 1, wherein inthe step (d), the modified region is formed into the substrate.
 5. Themethod according to claim 1, wherein in the step (d), the laser isirradiated from the back surface of the semiconductor wafer.